Push-pull control cable

ABSTRACT

A push-pull type control cable having a conduit tube and an inner cable comprised of a core wire and a plurality of strands wound around the core wire and inserted into the conduit tube, the control cable being filled with lubricant at a clearance between an inner periphery of the conduit tube and an outer periphery of the inner cable, wherein the plurality of strands each are comprised of three pieces of twisted element wires.

BACKGROUND OF THE INVENTION

1. This application is a divisional application based on claim 6 of thepending application Ser. No. 09/235,761 filed on Jan. 25, 1999.

FIELD OF THE INVENTION

2. The present invention relates to a push-pull control cable fortransmitting an operation effort in pushing and pulling directions.

DESCRIPTION OF THE PRIOR ART

3. In Japanese Patent Laid-open Publication No. 7(1995)26646, there hasbeen proposed a push-pull type control cable including an inner cablecomprised of a plurality of strands each formed by more than five piecesof twisted element wires and wound around a core wire, the inner cablebeing inserted into a conduit tube to be displaced in an axial directionfor transmitting an operation effort applied to its one end at apush-side or a pull-side. In use of the control cable, lubricant isfilled in a clearance between the inner periphery of the conduit tubeand the outer periphery of the inner cable to reduce friction of theinner cable in the conduit tube thereby to enhance load efficiency anddurability of the control cable. In the conventional control cable,however, a sufficient amount of lubricant may not be filled in theclearance between the inner cable and the conduit tube. As a result, theenhanced load efficiency and durability of the control cable may not bemaintained for a long period of time.

SUMMARY OF THE INVENTION

4. An object of the present invention is to provide a push-pull typecontrol cable the load efficiency and durability of which are maintainedin an enhanced condition for a long period of time.

5. According to the present invention, the object is accomplished byproviding a push-pull type control cable having a conduit tube and aninner cable comprised of a core wire and a plurality of strands woundaround the core wire and inserted into the conduit tube, the controlcable being filled with lubricant at a clearance between an innerperiphery of the conduit tube and an outer periphery of the inner cable,wherein the plurality of strands each are comprised of three pieces ofelement wires twisted in a manner of ordinary lay (twisted in a reversedirection relative to the winding direction of the strands. In thepush-pull type control cable, a sufficient amount of lubricant is filledin a clearance between the outer periphery of the inner cable and theinner periphery of the conduit tube since rugged surfaces larger inroughness are formed on the strands of the inner cable. This is usefulto maintain load efficiency and durability of the control cable in anenhanced condition for a long period of time. As the element wires eachare relatively large in diameter to enhance each bending stiffness ofthe strands in a small diameter, the buckling strength of the innercable can be increased to enhance operability of the control cable. Asthe outer peripheral area of the inner cable in contact with the innerperiphery of the conduit tube is reduced, friction of the inner cablecaused by displacement in the conduit tube can be decreased to enhancethe load efficiency of the control cable. In addition, the three piecesof element wires of each strand are twisted in such a manner that eachelement wire is pressed into contact with other two element wires tomaintain the configuration of each strand for a long period of time.

6. In actual practices of the present invention, it is desirable thatthe plurality of strands each are comprised of three pieces of elementwires twisted in a manner of ordinary lay (twisted in a reversedirection relative to the winding direction of the strands around thecore wire). In the strands of the inner cable, the element wires arestranded at a small angle relative to the axial direction of the innercable to enhance the buckling strength of the inner cable. As theelement wires appeared on the inner cable are aligned in parallel in theaxial direction of the inner cable, the friction of the inner cablecaused by displacement in the conduit tube is reduced to enhance theload efficiency and durability of the control cable.

7. In actual practices of the present invention, the plurality ofstrands may be provided in the form of a plurality of first strands eachcomprised of twisted element wires of large diameter twisted in a mannerof ordinary lay (twisted in a reverse direction relative to the windingdirection of the first strands and a plurality of second strandscomprised of element wires of small diameter twisted in the same manneras in the first strands, wherein the first and second strands arealternately wound around the core wire. With such an arrangement, asufficient amount of lubricant can be filled in a clearance between thesecond strands and the inner periphery of the conduit tube to maintainthe load efficiency and durability of the control cable in an enhancedcondition for a long period of time. In addition, the load efficiency ofthe control cable is further enhanced as the outer peripheral area ofthe inner cable in contact with the inner periphery of the conduit tubeis reduced.

8. In actual practices of the present invention, the plurality ofstrands may be provided in the form of a plurality of first strands eachcomprised of three pieces of element wires twisted in a manner ofordinary lay and a plurality of second strands each comprised of threepieces of element wires twisted in a manner of langs lay (twisted in thesame direction as the winding direction of the strands on the corewire), wherein the first and second strands are alternately wound aroundthe core wire. With this arrangement, the operability, load efficiencyand durability of the control cable can be enhanced, and the elasticityof the inner cable can be enhanced since the angle of the element wiresrelative to the axis line of the inner cable is increased.

9. In the above arrangement, the first strands each may be comprised ofstranded element wires of large diameter, while the second strands eachmay be comprised of twisted element wires of small diameter. With thisarrangement, a sufficient amount of lubricant can be filled to maintainthe load efficiency and durability of the control cable in an enhancedcondition for a long period of time. In this case, the friction causedby axial displacement of the inner cable in the conduit tube is reducedsince only the first strands formed in the ordinary lay are in contactwith the inner periphery of the conduit tube. This serves to enhance theelasticity of the control cable without causing deterioration of theload efficiency and durability.

10. Furthermore, the push-pull type control cable may be provided in theform of a control cable having an inner cable comprised of a strandformed by three pieces of twisted element wires and a single wire ofsmall diameter alternately wound around a core wire and inserted into aconduit tube, the control cable being filled with lubricant at aclearance between an inner periphery of the conduit tube and an outerperiphery of the inner cable.

BRIEF DESCRIPTION OF THE DRAWINGS

11.FIG. 1 is a view showing a component of a push-pull type controlcable in a preferred embodiment of the present invention;

12.FIG. 2 is a cross-sectional view of the control cable;

13.FIG. 3 is a perspective view of a first modification of the innercable shown in FIG. 1;

14.FIG. 4 is a cross-sectional view of the first modification;

15.FIG. 5(a) is a second modification of the inner cable shown in FIG.1, FIG. 5(b) is a cross sectional view of a control cable shown in FIG.5(a);

16.FIG. 6 is a third modification of the inner cable shown in FIG. 1;

17.FIG. 7 is a fourth modification of the inner cable shown in FIG. 1;and

18.FIG. 8 is a cross-sectional view of the fourth modification.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

19. Hereinafter, a preferred embodiment of the present invention will bedescribed with reference to the drawings. FIG. 1 illustrates a componentof a push-pull control cable in the preferred embodiment, and FIG. 2illustrates a cross-section of the control cable. The control cable iscomposed of a conduit tube 10 and an inner cable 20.

20. The conduit tube 10 is comprised of a liner 11 in the form of ahollow cable of synthetic resin, a plurality of strands 12 each formedby twisted element wires (for example, plated hard steel wires,stainless wires, etc.) and wound around the liner 11 and a jacket ofsynthetic resin covering the strands 12. The conduit tube 10 is flexiblein its entirety.

21. The inner cable 20 is comprised of a core wire 21 and a plurality ofstrands (in this embodiment, ten pieces of strands) wound around thecore wire 21. The inner cable 20 is flexible in its entirety andinserted into the liner 11 of conduit tube 10. The core wire 21 is madeof a material superior in straightness (for example, a stainless wire,an oil-temper wire, a bluing wire, a heat-stretch wire, a piano wire,etc.). The strands 22 each are comprised of three pieces of elementwires 22 a (for example, plated hard steel wires, stainless wires, etc.)twisted in a manner of ordinary lay. As shown in FIG. 2, a clearancebetween the outer periphery of inner cable 20 and the inner periphery ofliner 11 of conduit tube is filled with an amount of lubricant such asgrease G.

22. In the push-pull type control cable, the inner cable in conduit tubeis displaced by an operation effort applied at one end at a push-side orpull-side for transmitting the operation effort to the other end. Insuch an instance, each strand 12 of the conduit tube 10 acts to enhancebending stiffness of the conduit tube 10 for supporting displacementreaction of the inner cable 20, and the grease G serves to reducefriction of the inner cable 20 in the conduit tube 10. This is useful toenhance the load efficiency and durability of the control cable. In thecontrol cable, it is to be noted that the strands 22 each are comprisedof three pieces of element wires twisted to form rugged surfaces largerin roughness than those in a conventional push-pull type control cable.With such construction of the strands 20, a sufficient amount of greaseG can be filled in the clearance between the inner cable 20 and theliner 11 of conduit tube 10. This is useful to maintain the enhancedload efficiency and durability of the control cable for a long period oftime.

23. As the element wires 22 a each are relatively large in diameter toenhance each bending stiffness of the strands 22 in a small diameter,the buckling strength of the inner cable 20 can be increased to reducebacklash of the control cable. As the outer peripheral area of the innercable 20 in contact with the inner periphery of the conduit tube 10 isreduced, the friction of inner cable 20 caused by displacement in theconduit tube 10 can be decreased to enhance the load efficiency of thecontrol cable. In addition, the three pieces of element wires 22 a ofthe respective strands 22 are twisted in such a manner that each elementwire is pressed into contact with other two element wires to maintainthe configuration of each strand 22 for a long period of time.

24. In each of the strands 22, the element wires 22 a are twisted in amanner of ordinary lay at a small angle relative to the axial directionof the inner cable 20 to enhance the buckling strength of the innercable 20. As the element wires 22 a exposed on the inner cable 20 arealigned in parallel in the axial direction of inner cable 20, thefriction of inner cable 20 caused by displacement in the conduit tube 10is reduced to enhance the load efficiency and durability of the controlcable.

25. Hereinafter, first to fourth modifications of the above embodimentwill be described with reference to the drawings.

26. First modification:

27. Illustrated in FIG. 3 is a first modification of the control cablewherein an inner cable 30 is substituted for the inner cable 20 in thepreferred embodiment. FIG. 4 illustrates a cross-section of the controlcable in the first modification. The inner cable 30 is comprised of acore wire 31 of material superior in straightness similar to the corewire 21 of the inner cable 20 and a plurality of first and secondstrands 32 and 33 alternately wound around the outer periphery of corewire 31. The inner cable 30 is flexible in its entirety and insertedinto the liner 11 of conduit tube 10. Similarly to the strands 22 of theinner cable 20, the first strands 32 each are comprised of three piecesof element wires 32 (for example, plated hard steel wires, stainlesswires, etc.) twisted in a manner of ordinary lay, while the secondstrands 33 each are comprised of three pieces of element wires 33 atwisted in a manner of ordinary lay. The element wires 33 a each aremade of the same material as the element wires 32 a and formed smallerin diameter than the element wire 32 a to provide the second strands 33each slightly smaller in diameter than the first strands 32.

28. In the push-pull type control cable described above, the sameeffects to those in the preferred embodiment can be expected since thefirst and second strands 32 and 33 each are comprised of three pieces ofelement wires 32 a, 33 a respectively twisted in a manner of ordinarylay. As the second strands 33 in the control cable each are formedsmaller in diameter than the first strands 32, a sufficient amount ofgrease G can be filled in a clearance between the second strands 33 andthe liner 11 of conduit tube 10 to maintain the load efficiency anddurability of the control cable in an enhanced condition for a longperiod of time. As the outer peripheral area of inner cable 30 incontact with the inner periphery of conduit tube 10 is smaller than theouter peripheral area of inner cable 20 in contact with the innerperiphery of conduit tube 10, the load efficiency of the control cableis further enhanced.

29. Second modification:

30. Illustrated in FIG. 5 is a second modification of the control cablewherein an inner cable 40 is substituted for the inner cable 20 in thepreferred embodiment. The inner cable 40 is comprised of a core wire 41of the same material superior in straightness as that of the core wire21 in the inner cable 20 and a plurality of first and second strands 42and 43 (for example, five pieces of strands) alternately wound aroundthe core wire 41. The inner cable 40 is flexible in its entirety andinserted into the conduit tube 10. The first strands 42 each arecomprised of three pieces of element wires 42 a (for example, platedhard steel wires, stainless wires, etc.) twisted in a manner of ordinarylay as well as the strands 22 of the inner cable 20, while the secondstrands 43 each are comprised of three pieces of element wires 43 atwisted in a manner of langs lay.

31. In the push-pull type control cable described above, the sameeffects as those in the preferred embodiment can be expected since thefirst and second strands 42 and 43 each are comprised of three pieces ofelement wires 42 a, 43 a and the first strands 42 are formed in theordinary lay. As the second strands 43 in the control cable each areformed in the langs lay so that the angle of the element wires 43 arelative to the axis line of inner cable 40 is increased, the elasticityof inner cable 40 can be enhanced.

32. Third modification:

33. Illustrated in FIG. 6 is a third modification of the control cablewherein an inner cable 50 is substituted for the inner cable 20 in thepreferred embodiment. In this modification, the inner cable 50 iscomprised of a core wire 51 of the same material superior instraightness as that of the core wire 21 of inner cable 20 and aplurality of first and second strands 52 and 53 (for example, six piecesof strands) alternately wound around the core wire 51. The inner cable50 is flexible in its entirety and inserted into the conduit tube 10.The first strands 52 each are comprised of three pieces of element wires(for example, plated hard steel wires, stainless wires, etc.) 52 atwisted in a manner of ordinary lay as well as the strands 22 of innercable 20, while the second strands 53 each are comprised of three piecesof element wires 53 a twisted in a manner of langs lay. The elementwires 53 a are made of the same material as that of the element wires 52a and formed smaller in diameter than the element wires 52 a to providethe second strands 53 slightly smaller in diameter than the firststrands 52.

34. In the push-pull type control cable described above, the sameeffects as those in the preferred embodiment can be expected since thefirst and second strands 52 and 53 in the control cable each arecomprised of three pieces of element wires 52 a, 53 a and the firststrands 52 are formed in the manner of ordinary lay, and the sameeffects as those in the first modification can be expected since thesecond strands 53 each are formed smaller in diameter. In addition, theelasticity of the control cable can be enhanced as in the secondmodification since the second strands 53 each are formed in the langslay. In this modification, the friction caused by axial displacement ofthe inner cable 50 in the conduit tube 10 is reduced less than that inthe second modification since only the first strands 52 formed in theordinary lay are in contact with the inner periphery of liner 11 ofconduit tube 10. This serves to enhance the load efficiency anddurability of the control cable.

35. Fourth modification:

36. Illustrated in FIG. 7 is a fourth modification of the control cablewherein an inner cable 60 is substituted for the inner cable 20 in thepreferred embodiment. FIG. 8 illustrates a cross-section of the controlcable in this modification. The inner cable 60 is comprised of a corewire 61 of the same material superior in straightness as the core wire21 of inner cable 20, a plurality of strands 62 and single wires 63 eachalternately wound around the core wire 61. The inner cable 60 isflexible in its entirety and inserted into the liner 11 of conduit tube10. The strands 62 each are comprised of three pieces of element wires(for example, plated hard steel wires, stainless wires, etc.) twisted ina manner of ordinary lay as well as in the strands 22 of inner cable 20,while the single wires 63 each are made of the same material as that ofthe element wires 62 a and is formed slightly smaller in diameter thaneach of the strands 62.

37. In the push-pull type control cable described above, the sameeffects as those in the preferred embodiment can be expected since thestrands 62 each are comprised of three pieces of element wires 62 atwisted in the ordinary lay, and the same effects as those in the firstmodification can be expected since the single wires 63 each are formedsmaller in diameter than each of the strands 62.

38. Although in the fourth modification, the strands 62 each have beenformed in the ordinary lay to enhance mainly the operability, durabilityand load efficiency of the control cable, a portion or the entirety ofthe strands 62 may be formed in the langs lay to enhance the elasticityof the control cable.

What is claimed is:
 1. A push-pull type control cable having an innercable comprised of a strand formed by three pieces of twisted elementwires and a single wire of small diameter alternately wound around acore wire and inserted into a conduit tube, the control cable beingfilled with lubricant at a clearance between an inner periphery of theconduit tube and an outer periphery of the inner cable.